The present invention relates in general to an information recording system capable of writing and reading information on and from a rotatable data-storage medium such as a recording disk, and more particularly to power switching arrangements for selective power supply, for maximum energy saving, to electrically operated elements used in a read/write device.
For recording or writing information on an information storage medium, there has been used a transducer head, such as a magnetic head that transforms electric variations into magnetic variations for storage on magnetic media, or a laser head that emits modulated laser beam for storage on optical media, magneto-optical media, etc.
In writing or reading information, the transducer head of the recording system must be moved relative to a rotatable recording medium substantially radially of the medium. For this purpose, a known magnetic recording system, for example, uses a drive unit for moving and positioning a magnetic head radially with respect to a rotatable magnetic data-storage medium. The magnetic recording system uses other electrically operated elements, which include: reading and writing amplifiers for amplifying input and output signals to and from the magnetic head, which signals represent input and recorded information to be written on or read from the data-storage medium; and detectors for sensing the operating conditions of the recording system such as the angular position of the data-storage medium and the reference position of the magnetic head, in order to control the recording system according to the signals from these detectors. Other types of information recording systems using a magneto-optical or other transducer head, also employ such electrically operated elements as indicated above.
Heretofore, it has been the practice to keep electric power supplied to these electrically operated elements irrespective of the need to operate the individual elements. For example, the windings of a drive motor for moving the magnetic head relative to the rotatable magnetic data-storage medium are kept energized in a given phase of excitation which was established at the end of a previous operation of the drive motor. Therefore, the power is continuously consumed by the drive motor even while the magnetic head is positioned at a given track of the data-storage medium during a period of data reading from, or writing or erasing on the data-storage medium.
Similarly, the electric power is applied to both of the reading and writing amplifiers even while the magnetic head is not operating to write or read information on or from the magnetic recording medium. Further, the electric power is generally applied to the reading amplifier while a writing or erasing operation is effected by the magnetic head. Conversely, the power supply to the writing amplifier is maintained during a reading operation of the recording system. In the same way, the electric power is always applied to the various detectors as long as the recording system is on.
However, the power supply to such electrically operated elements of the recording system is not always needed. Stated more specifically, it is not necessary to maintain the power supply to the magnetic head positioning motor while the magnetic head is performing a reading, writing or erasing operation at a selected track of the magnetic recording medium. Consequently, the conventional arrangement to keep the power supply to the head drive motor even during a data reading, writing or erasing operation of the magnetic head, will result not only in unnecessary consumption of power, but also in increased heat generation from the drive motor, which causes various troubles such as shortening of the service life of the drive motor.
It is also recognized that the power supply to the reading and writing amplifiers, and to the detectors is not always required. That is, the power supply to such components is required only when their operation is needed. In more detail, the reading amplifier, for example, should be supplied with power only when the magnetic head operates to read information from the magnetic data-storage medium, or the detector for sensing the angular position of the data-storage medium requires electric power only when it is necessary to check the angular position of the data-storage medium. The power supply to such components at other opportunities is useless, and leads to an increase in the power consumption of the recording system as a whole. In the case where the recording system is powered by a battery, this increase in the power consumption will unnecessarily shorten the battery life.